Flourescence sensing device

Abstract

A fluorescence sensing device for determining the presence or concentration of an analyte in a liquid or gaseous medium is constructed of an optical filter, which is positioned on a photodetector and which has a thin film of analyte-permeable, fluorescent indicator molecule-containing material on its top surface. An edge-emitting, light-emitting P-N junction is positioned on the top surface of the optical filter such that the P-N junction from which light is emitted is positioned within the film. Light emitted by the fluorescent indicator molecules impacts the photodetector thereby generating an electrical signal that is related to the concentration of the analyte in the liquid or gaseous medium. Fluorescence sensing devices according to this invention are characterized by very compact sizes, fast response times and high signal-to-noise ratios.

What is claimed is: 
     
       1. A fluorescence sensing device for determining the presence or concentration of an analyte in a liquid or gaseous medium comprises (a) an optical filter having substantially flat, parallel top and bottom surfaces;   (b) a film of analyte-permeable fluorescent matrix on the top surface of the optical filter, said matrix containing fluorescent indicator molecules whose fluorescence is modulated by the presence of analyte in said film;   (c) a light-emitting P-N semiconductor junction which emits light at a wavelength that excites fluorescence in the indicator molecules; said light-emitting P-N junction being positioned on the top surface of the optical filter such that at least a portion of the light is emitted within the fluorescent matrix in directions substantially parallel to the top surface of the optical filter; and   (d) a photodetector on the bottom surface of the optical filter which generates an electrical signal responsive to fluorescent light emitted by said fluorescent indicator molecules; wherein the optical filter has a relatively low absorbance for fluorescent light emitted by said fluorescent indicator molecules and a relatively high absorbance for light emitted by said light-emitting P-N junction.     
     
     
       2. The fluorescence sensing device of claim 1, wherein the fluorescent matrix film has a depth of from about 500 Å to about 200 microns. 
     
     
       3. The fluorescence sensing device of claim 1, wherein the fluorescent matrix film has a depth of from about 10 microns to about 100 microns. 
     
     
       4. The fluorescence sensing device of claim 1, wherein the top surface of the optical filter has a recessed area having a depth and diameter sufficient to contain the fluorescent matrix film. 
     
     
       5. The fluorescence sensing device of claim 1, wherein the light-emitting P-N junction is a light-emitting diode and is positioned in a pocket in the top surface of the optical filter such that the P-N junction is positioned at about the center of the thickness of the analyte-permeable material. 
     
     
       6. The fluorescence sensing device of claim 1 or 5, wherein a moat is cut into the top surface of the optical filter, surrounding the light-emitting P-N junction, and serves to stop the spread of the fluorescent matrix when it is applied in liquid form. 
     
     
       7. The fluorescence sensing device of claim 1, wherein the fluorescent matrix is a polymer which contains fluorescent indicator molecules. 
     
     
       8. The fluorescence sensing device of claim 7, wherein the polymer is a silcone polymer. 
     
     
       9. The fluorescence sensing device of claim 7, wherein the indicator molecule is the complex, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate, and the fluorescence sensing device is an oxygen sensing device. 
     
     
       10. The fluorescence sensing device of claim 9, wherein the optical filter has a wavelength cutoff of about 610 nm. 
     
     
       11. A fluorescence sensing device for determining the presence or concentration of an analyte in a liquid or gaseous medium comprises (a) an optical filter having substantially flat, parallel top and bottom surfaces;   (b) a film of waveguide material on the top surface of the optical filter, said waveguide material having a refractive index greater than that of said liquid or gaseous medium and said waveguide material having on the surface thereof fluorescent indictor molecules whose fluorescence is modulated by the presence of analyte;   (c) a light-emitting P-N semiconductor junction which emits light at a wavelength that excites fluorescence in the indicator molecules; said light-emitting P-N junction being positioned on the top surface of the optical filter such that at least a portion of the light is emitted within the waveguide, such that it is largely propagated within the waveguide and excites fluorescence in the indicator molecules on the surface of the waveguide; and   (d) a photodetector on the bottom surface of the optical filter which generates an electrical signal responsive to fluorescent light emitted by said fluorescent indicator molecules, wherein the optical filter has a relatively low absorbance for fluorescent light emitted by said fluorescent indicator molecule and a relatively high absorbance for light emitted by said light-emitting P-N junction.